Diaphrage screen



March 28, 1944. c, L. SPAFFORD DIAPHRAGM SCREEN Filed April 9, 1942 non/n. F m TP mm 2 w Patented Mar. 28, 1944 Claude L. Spafford, Sherbrooke,

Quebec, Canada,

assignor to Sherbrooke Machineries Limited, Sherbrooke, Quebec, Canada Application April 9, 1942, Serial No. 438,316

' Claims.

This invention relates to diaphragm screens used in the pulp and paper industry and the I main object is to provide improved means whereby the screen plates are removably clamped in place and sealed against leakage.

In the conventional diaphragm screen the marginal portions of the screen plates rest on underlying supports carried by the vat and are held down by overlying sealing strips which are fastenedto the vat walls by wood screws. These sealing strips must be removed at fairly frequent intervals to provide for repair or replacement of the screen plates or to give access to the underlying diaphragms. This takes considerable time since it involves the removal of a number of wood screws and the subsequent replacement of the sealing strips so that the fastening screws may be re-engaged in the same openings in the vat wall from which they were withdrawn.

Another objection to the conventional arrangement is that the wood screws holding the sealing strips" in place become loose and permit leakage to'take place between the sealing strips and the marginal portions of the screen plates and also between the marginal portions of the screen plates and the underlying supports on which the plates rest. This loosening'of the screens and sealing strips is due, partly, to enlargement of the screw holes by frequent removal and replacement of the screws and partly to pressure exerted on the sealing strips by flexure of the screen plates due to the pumping action of the diaphragm. Attempts to remedy this difficulty by interposing felt and other sealing material between the sealing strips and the underlying marginal portions of the screen plates have not proven entirely satisfactory.

According to the present invention the foregoing diillculties are overcome by substituting for the conventional wood screws easily removable clamping devices by means of which down ward pressure is exerted on the sealing strips so as to force them tightly against the underlying marginal portions of the screen plates and this, in turn, causes the marginal portions of the screen plates to be pressed tightly against their underlying supports. This arrangement makes it possible to provide an effective seal at all points along the marginal portions of the plates which are engaged by the sealing strips and it also makes it impossible for the plates to be loosened by the flexing stresses imposed thereon by the pumping action of the underlying diaphragm.

Another feature of the invention consists in 55 strips and the end portions f the constructing and arranging the sealing strip clamping devices so that they permit the mounting and removal of the sealing strips and screen plates to be easily and quickly accomplished, thus making it possible to repair or replace the screen plates or the underlying diaphragms with the least possible shut down Or delay.

Other objects, advantages and characteristic features of the invention will be more readily apparent from the following detailed description taken in connection with the accompanying drawing, in which Fig. 1 is a sectional view of a diaphragm screen embodying my invention, the right hand half of this view being a section substantially along the line A-A of Fig. 2 and the left hand half being a section substantially along the line 3-3 of Fig. 2.

Fig. 2 is a sectional view Fig. 1.

Fig.3 is a detailed view of one of the clamping members shown in the preceding figures.

along the line 2-2 of V Fig. 4 is a sectional view illustrating a slight modification of the invention as applied to a .wooden vat.

Fig. 5 is an elevational view of the abutment ilate forming part of the assembly shown in Fig. 4.

In Figs. 1 to 3, inclusive, I have shown a diaphragm screenin which the vat 5 and the diaphragm frame 6 are made of metal, the diaphragms I being fastened to conventional diaphragm actuating mechanism indicated at 8. The screen plates and the sealing strips are respectively indicated at I!) and II. The ends of each plate l0 are pressed firmly against underlying bars or supports 12 by the sealing strips II which are clamped in place by my improved clamping devices generally indicated at Hi. The side portions of each plate l0 rest on stationary supports or bars M and I5 and are provided withbevelled edges 16 and H. The edge I! is fitted against a mating undercut bevelled portion l8 of bar 15 while the edge I6 is fitted against an undercut bevelled edge IQ of a removable locking bar 20 which is fitted between two adjacent bars I4 and is held down by clamping screws 2|.

The sealing strips H are free of direct attachment to the adjacent upright walls of the vat 5 but are held against said walls by the clamping devices 13 which also serve to exert a considerable amount of downward pressure on the sealing strips whereby a tight seal is obtained between the lower edges of the sealing plates I0 and between the end portions of the plates and the underlying plate supports or bars I2.

As here shown each clamping device l3 comprises a hollow clamping member 25 provided with a bevelled lower edge 26 which matches and engages the bevelled upper edge 21 of one of the sealing strips, the inclination of the engaging bevelled surfaces 26 and 2! being such as. to hold the sealing strip tightly against the adjacent upright wall of the vat when downward pressure is applied to the hollow clamping member 25 screws 42 by the upward thrust or pressure of the clamping nuts '44 against the plates 4|, each lower end of bolt 28 is fitted with a nut 35 which is screwed tightly against an abutment surface 36 provided at the lower end of the bolt hole fitting 34, said abutment surface'being inclined so as to lie in a plane which is perpendicular to the central axis of the inclined bolt hole 33.

When the clamping nut 35 of each clamping device I3 is tightened against the adjacent abutment surface 38 the downward and outward pull of the bolt 28 causes the associated clamping member to exert-downward pressure on the underlying sealing strip ll, thus forcing the lower edge of the sealing strip tightly against the subiacent ends of thescreen plates In.

when it is desired to remove the screen plates this may be accomplished by backing off the clamping nuts of the clamping devices l3 so as to release the clamping pressure on the sealing strips H sufliciently to permit these strips to be pulled from beneath the clamping members 25.

'After the sealing strips have been removed the locking bars 20 and their associated clamping screws 2| are then removed to complete the releasement of the plates it which may then be taken out of the vat for replacement or repair purposes or to give access to the underlying diaphragm. Alternately, the sealing strips ll may be freed for removal by first removing the nuts 35 of the clamping devices l3 and then completely removing the clamping members 25 and bolts 28.

In some types of diaphragm screens the four edges of each screen plate are held downbysealing strips such as indicated at II. In connection with screensof this type it will be understood that each sealing strip will be clamped in place by a plurality of clamping'devices of the type indicated at l3.

In Figs. 4 andv 5 my invent n is shown applied to. atype ofscreen .in which the screenvat 39 and the screen plate supports 40 are made of wood. In this case pressure applying bolts 230 are passed through downwardly and outwardly inclined bolt holes 33awhich are drilled through the wooden walls of the vat. The bolts 28:: also, extend through the bolt holes 40 of metal plates 4| which are fastened to the outer surfaces of the v'at walls by wood screws 42. These plates 4| are formed with inclined abutment surfaces 43 which correspond to the previously mentioned-abutment surfaces 36 and areengaged by the bolt tightening nuts 44. In order to prevent loosening of the of said plates is provided with a horizontal lug 48 which bears against the flat top 41 of a recess which is formed in the vat wall by an upward enlargement of the lower end of the bolt hole 330.

As shown to advantage in Fig. 4, the clamping nut 44 is formed with a convexly curved sphericalbearing surface a whichifits against a concavely curved spherical portion 43a of the abutment surface 43. These engaging spherically curved surfaces provide a very desirable ball and socket connection between the bolt 28a and the plate 4|.

The design of the vat shown in Figs. 1 and 2 is such that, when the screen plates in and locking bars 23 are removed, the diaphragms may be repaired or replaced without otherwise disturbing the vat.

Having thus described'whatl nowconsider to be the preferred embodiment of this invention, it will be understood that various modifications maybe resorted to withinthe scope and spirit of the appended claims.

Having thus described my invention, what I claim is:

1-. A diaphragm pulp'screen comprisinga vat provided with screen plate supports, screen plates arranged in said vat withmarginal edges thereof resti g on said supports, sealing strips overlying supported edgesof said plates and a plurality of removable clamping .devices engaging the upper edge of each-sealing strip and exerting downward pressure thereon, each of said clamping devices comprising a hollow clamping member resting on the upper edge of one of said sealing strips, a pressure applying bolt having its upper end fitted in cavity in said clamping "member and provided with a cross pin having its ends removably fitted in grooves provided in opposite side walls of said cavity, said bolt extending-dowm' wardly and outwardly through an inclined bolt opening provided in a side wall portionof the vat, a nut threaded onto the lower end of the bolt and means at the lower end of the boltopening affording an abutment surface for said nut.

2. A pulp screen plate clamping means for diaphragm screens comprising a clamping member provided with a. bolt head receiving cavity'having an entrance opening for the insertion of a bolt head, the side wallsof said cavity being provided with grooves extending inwardly and downwardly from said entrance opening, said grooves being open at their outer or upper endsand being closed at their inner or lower endsand a bolt, the head portion of which is adapted to befitted in said cavity and is provided witha transversely extending pin, the ends of which project beyond opposite sides of the head portion and are adapted to be received in said grooves, said bolt having a nut threaded thereon at the end remote from said Din.

3. A pulp screen plate clamping means as set forth in claim 2 including a plate adapted'to be assembled with said bolt to provide an abutment for said nut, said plate having'a boltopening therein and being provided, at one side thereof, with an abutment surface which is inclined so as to lie. in a plane which is perpendicular to the central axis of the bolt opening of the plate.

to the outer surfaces of said walls, screen plate supports arranged in said vat below the upper ends of said holes, screen plates arranged in said vat with edges thereof resting on said supports, sealing strips overlying the supported edges of said plates, a plurality of hollow clamping members overlying and engaging the upper edge of each sealing strip, each clamping member being provided with a. bolt-head receiving cavity overlying and communicating with the upper end of one of said bolt holes, a plurality of bolts, each having its head portion detachably secured in place within the cavity of one of said clamping members and its shank portion extending downwardly and outwardly through the bolt hole communicating with said cavity, clamping nuts threaded onto the lower ends of said bolts and means at the lower ends of. the bolt holes affording abutment surfaces against which said nuts are tightened to pull the bolts downwardly and thereby cause said clamping members to exert downward pressure on said sealing strips.

5. A diaphragm pulp screen as set forth in claim 4, in which each of said abutment surfaces lies in a general plane substantially perpendicular to the central axis of the associated bolt hole.

CLAUDE L. SPAFFORD. 

